I think that this dichotomy can be summarized with the old logical identity: A or B = not(A) implies B Considered as a statement about types, 'A or B' is a va

I think that this dichotomy can be summarized with the old logical identity: A or B = not(A) implies B Considered as a statement about types, 'A or B' is a variant type over two constructors A/B (this is equivalent to an optional type, where A=unit). Also as a statement about types, 'not(A) implies B' is a function taking a continuation on A (the exception handler) and returning a B (if it decides not to raise an exception). So (as we often find in CS) this is a very old idea, older than computers and programming languages. :D